Basic Wiring Question

[strummer]

First off, please forgive the "elementary" level of this question. 
Although I've been an "armchair" modeler for 40(!) years, I only recently acquired the room to actually have a layout, so I have little knowledge about such things as wiring for operation.
I plan on having a couple of reverse loops. Now, I recall Atlas sold something at one time (a little box with a couple of slide switches) that was designed for such a situation. Perhaps it was called a "Controller"?
I have (2) power packs: an MRC "ControlMaster VI" and the Heathkit RP-1065: both have a switch and track outputs marked "Reverse Loop".
Does this mean these built-in circuits will do the same thing the Atlas product was designed for?
Again, sorry for asking such a basic question....

Mark in Oregon

[jagged ben]

The Atlas Controller is the correct product for controlling a reverse loop and selecting between two cabs.  I found a diagram online for the Heathkit which shows that it can control a reverse loop but only for one cab.  I couldn't find info on that MRC but I would guess it is similar.  If you want to use both your power packs to run two trains at once then the Controller is an easy way to go.  You'll need one Controller for each reverse section.  You'll also need a Selector or some DPDT switches to switch the mainline between the two powerpacks.

If you only plan to ever run one train, you could probably just use the Heathkit and hook all reverses to it's reverse output.

[strummer]

Thanks Ben

I will search for the link you found...

Here's something else. The MRC pack has a (2) direction switches: one each for both "main" and "loop". The Heathkit also has both of those, but features a third direction switch, labeled "Engine Direction". WTF? Would that be for a reverse loop situation?

I bought the "Assem & Operator Manual" but it's pretty vague on that point...(I guess they figured anyone savvy enough to build it would already know these things...)

Mark in Oregon

[glakedylan]

here's a diagram of the heathkit:
https://www.nostalgickitscentral.com/heath/schematics/heathkit_schema_rp1065.pdf
it indicates two sets of outlets, with two each
one for main (+ and - terminal)
one for loop (+ and - terminal)
two for accessories (2+ and 2- terminals)
@peteski would be able to give more information on the schematic
the MRC indicates
https://thumbs.worthpoint.com/zoom/images4/1/0215/14/mrc-transistorized-controlmaster-vi_1_29e8623d8ab7df313d1c675826498bd5.jpg
(main, reverse, AC accessories, fixed voltage DC accessories)
hope this helps
sincerely
Gary

[peteski]

The engine direction switch controls the polarity of the throttle voltage. the output from that switch is then fed to both main and loop direction switches.  Then each of those switches can flip the polarity of what is coming from the engine switch.

Basically, you should use the engine direction to control which direction the engine is running.  Then leave the main switch alone and use that for running your layout. If you have a reverse loop then power it from the loop output (and control the loop polarity with the lop switch).

To put it another way, if the loco is running from the main output, either engine direction or the main switch will flip the engine's direction.
If the loco is running from the loop output, either engine direction or the loop switch will flip the engine's direction.

[strummer]

...so if I have the main part of the layout wired to the "main" output, and wire the insulated part of the loop to the "loop" contacts, then once the engine is in the loop section, I reverse the main switch and as the train leaves the loop every thing will be OK, because the train is now going in the opposite direction(?). And I would leave the "engine direction" switch alone?

Thanks for bearing with me on this... 

Mark in Oregon

[peteski]

...so if I have the main part of the layout wired to the "main" output, and wire the insulated part of the loop to the "loop" contacts, then once the engine is in the loop section, I reverse the main switch and as the train leaves the loop every thing will be OK, because the train is now going in the opposite direction(?). And I would leave the "engine direction" switch alone?

Thanks for bearing with me on this... 

Mark in Oregon

Well . . .

If the polarity of the loop is already the same as the polarity of the main at the point (turnout) where the engine enters the loop then you can leave the switches alone until you get close to the exit of the loop. If not make the loop the same polarity as main. Then line up the reverse loop turnout for exit.  At this point the loop and main polarity is opposite so you cannot continue driving the train past the turnout.

Now you have 2 options:

1. Flip the main switch and the engine will now continue traveling in the correct direction past the reverse loop exit (but for all the intensive purposes the main will now have reversed polarity of what it was before you entered the reverse loop - which should be irrelevant for the overall layout operation).  I think that is how the designers of the throttle meant for the throttle to operate reverse loops.

2. Flip the loop switch and the engine direction switch, and leave the main switch alone.

Either option will give you correct results.

[jagged ben]

...so if I have the main part of the layout wired to the "main" output, and wire the insulated part of the loop to the "loop" contacts, then once the engine is in the loop section, I reverse the main switch and as the train leaves the loop every thing will be OK, because the train is now going in the opposite direction(?). And I would leave the "engine direction" switch alone?

Yes.   

[peteski]

Yes.   

I again over-explained. 

[strummer]

 Not for me! OK, but one more question:

The train is being headed by an SD40.

Let's say the train is in the "main" block, traveling west. I throw the "loop" switch so the polarity is the same, now also heading west.

Now the train is in the insulated "loop" section. I then switch the "main" section to head east, and align the turnout.

When my train gets to the point where the main and loop merge, as the loco crosses the insulated joiners, the front truck is back in the main section, and will be receiving current heading east, while the rear truck, which is still in the "loop" section is getting juice heading west.

How does that work? Wouldn't there be a short at that point, since one truck wants to go east and the other wants to go west??

Mark in Oregon

[mmyers]

Mark,
 Remember the train is going through a loop. It is entering going West. When it exits the loop, it is going East. Polarity must match when it exits. Using the compass. when it enters the loop going west, the rail to the north will be positive. South rail will be negative. By the time it gets to the other end of the loop, the same rail that was north now has to match the south rail of the main.
Martin Myers

[strummer]

Yes, I understand that: that's why I asked the question. I'll try again.

If I'm running a steam engine: as the loco re-enters the main after coming off the loop: the drivers are in the main block, while the tender's pick-up wheels are still in the loop block.

Why isn't there at short at that moment?

Mark in Oregon

[peteski]

Yes, I understand that: that's why I asked the question. I'll try again.

If I'm running a steam engine: as the loco re-enters the main after coming off the loop: the drivers are in the main block, while the tender's pick-up wheels are still in the loop block.

Why isn't there at short at that moment?

Mark in Oregon

Ok, here is a diagram which shows how this works. Of course both rails on both sides of the loop have to be gapped. Pay attention to the rail polarity and to the positions of the switches (well we are only flipping the MAIN switch).

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[strummer]

Thank you...

Mark in Oregon